Body Control ECU Module Issue

[Muddy Bean]

Hi Team.

Just purchased a 1998 LC w/factory center and rear diff locks. 107,000 miles. Brand new rubber all the way around and a new paint job (paint was faded from the Florida sun). Really enjoying the build quality. Chasing down two issues:

1. Body Control Module is flaky so door locks, dome lights don't operate without ignition turned on and high beams stay on when headlights are turned on.

2. CEL is on and throwing a code saying two O2 sensors (out of the four) need replacement.

Questions:
I have heavily searched the web and forum and haven't completely understood whether I can merely fool or unplug the rear o2 sensors. If so, I'd love any advice on that.
Based on my web research, the Body Control Module appears to be the culprit for the door lock/highbeams always on/dome lights not working when ignition is turned off issues. If I am wrong about this, please do let me know.
One last question...just was driving highway speeds and accidentally bumped the center diff lock button with my knee...immediately turned it off again...did I mess up my center diff by doing that? Is there a safety above a certain speed?

Thanks so much to all of you on the forum. Your collective knowledge has been super insightful over the last several months.

BTW, new to LC but not Toyota. Currently own a Camry with 262,000 miles and have owned a corolla, another camry and an 89 4WD pickup.

Scott

 

[Trunk Monkey]

Welcome. What leads you do the diagnosis that the body control ecu is bad? Not saying it's not, just wondering. Sounds like you have bigger electrical issues, maybe moisture in the kick panel fuse block.

For your O2 sensors, you can unplug them, but you will get a constant CEL from the ECU not being able to read those sensors post cat.

And for your CDL, no harm done. The truck will sense if it can lock and the dash light will blink until it locks, so it probably wasn't even long enough for it to engage.

 

[Muddy Bean]

Thanks for the reply! My research here on the forum led me to believe the Body ECU might be bad. Others with similar weird issues replaced theirs and solved all the problems. I removed the Body ECU yesterday and sprayed contact cleaner into the plugs and socket of the unit. After experimenting plugging in and unplugging the three plugs on the unit, I determined that indeed it controls the high beams, dome lights, and door locks as well as a host of other interior processes. Toyota of Orlando also had the truck for a day trying to figure out what was wrong and they also concluded it needed a Body Control Module/ECU. I can certainly check the kick panel fuses but I'm leaning towards a Body Control Module. As for the o2 sensor issue, I'm not bothered by the CEL at the moment, but I would like the truck to idle and accelerate without stumbling, so if the rear o2 sensors are causing this, could I alleviate the stumbling and rough idle by unplugging them for now until I get new sensors? Thanks again so much!

Scott

 

[Muddy Bean]

Sorry, I know you guys like pics so here's a couple:

 

[OregonLC]

How certain are you that it's the rear O2? It's way more common to have the front go out. The front control short term AFR trim and I'd suspect the vehicle will default to rich if unplugged which will hurt economy and damage the cats. I'd worry less about the rear, AFAIK they just observe cat efficiency (and throw a code). Personally, my OCD couldn't handle the CEL and I'd replace either but that's up to you to evaluate the risk.

 

[Muddy Bean]

Oregonlc,

Nice paint color all four are throwing a code, but two were already replaced by the stealership. They are showing intermittent. The other two were never replaced and are showing a full out of spec failure. I was told that those two failing are likely causing the other two to work intermittently. Not sure how true this is, but that's why I'm here. Thanks for the info on the o2 sensors. I'll confirm which ones are indeed throwing which codes. I'll refrain from unplugging too.

 

[Trunk Monkey]

If all 4 O2 sensors failed simultaneously, you've got other problems - or a crooked dealership.

 

[Muddy Bean]

Had the codes read again today this time at Autozone. Bank 1 and 2 are showing o2 sensor 1 heater circuits dead and a cylinder 5 misfire. The gentleman that helped me suggested that it's rare for two o2 sensor heater circuits to fail on both banks at the same time. He's thinking maybe a fuse. So, once again, to confirm, I have Bank 1 and 2 o2 sensor 1 heater circuit failure and a cylinder 1 misfire (which I can definitely feel). I'm going to chase down the misfire by switching out the coil/wire from cylinder 5 and swapping it with another one and see if the code switches to the swapped cylinder. If so, I need a new coil/wire for cylinder 5. Guess I have some fuse searching on my hands and will update as I go. Thanks for the advice!

 

[hoser]

I would physically take a look at the o2 sensors. The PO might have installed the wrong sensors. Maybe the wiring was jury rigged and melted?

 

[Muddy Bean]

I'll physically check them. Previous owner was an older lady (it's a one owner) who died. Her daughter sold the truck for her. She took it to the stealership for all the maintenance. I spent 30 minutes on the phone with the dealership she had it serviced at. They forwarded me the maintenance history. Two gremlins:

1. The o2 sensors
2. Body Control Module/ECU issue from a minor windshield leak after a new windshield was installed. Chasing that down.

 

[pwcummings]

Sounds like the old ladies ghost is wreaking havoc on that LC... Aside from the cels, how's she actually running? Hopefully you got a real good deal because this sounds like a bit of a headache!

 

[Muddy Bean]

That cylinder 5 occasional misfire is annoying, but when it's not doing that, she runs like a champ. Bought her in Florida with 100,000 miles. Body, frame, interior squeaky clean. (Florida truck) for $10,000. Works for me. He came clean with the issues. I was willing to take it because I have no problem chasing them down. Done it on nearly ever car I've owned. Paid $1,750 for a 1998 Camry and have driven it two years already...put nearly 70,000 miles on it. Nary a problem. The truck has always been a dream of mine. It just needs some love, an o2 sensor/fuse, ecu, and possibly some wires/plugs. That's why I'm here! To join the madness!

 

[Muddy Bean]

Turned out all the electrical issues were solved with one 15amp fuse in the kick panel. $1.50. Now to chase down the cylinder 5 misfire and o2 sensors and we're all set!

 

[Muddy Bean]

Revisit on this thread. Cylinder 5 misfire was due to a bag spark plug. Problem fixed about a month ago. Now down to just my rear O2 sensors. Both are reading heater circuit failure. Where is the fuse for those beasts located? It's my last gremlin. Truck is now perfect with a ECU B fuse replaced, spark plug replaced on cyl 5, and now down to these rear O2 sensors throwing my only code.